DOHA, Qatar (AP) — Sharp disagreements arose Sunday on the first day of a Syrian opposition conference meant to forge a more cohesive leadership that the international community says is necessary before it will boost its support for those trying to overthrow President Bashar Assad.

The main opposition group in exile, the Syrian National Council, balked at a U.S.-backed plan that would largely sideline it to make room in a new leadership council for fighters and activists inside Syria. However, with international pressure mounting, the SNC also suggested it is willing to negotiate a compromise that would give the SNC more influence in a new leadership team.

The international community has long urged the SNC, widely seen as dysfunctional and out of touch, to broaden its base and include a greater spectrum of Syrian society, especially those fighting inside the country. Last week, U.S. Secretary of State Hillary Rodham Clinton was unusually harsh, suggesting the SNC's leadership days are over.

Failure to reach a deal in Doha could further heighten tensions between Syria's political opposition and the international community. Opposition leaders feel abandoned by the U.S. and other foreign backers, saying they are not providing the money and weapons the rebels need to defeat Assad in a stalemated civil war. Washington and others say they can't step up aid unless the opposition stops bickering and establishes a more representative — and unified — leadership.

The conflict erupted nearly 20 months ago as a peaceful uprising that escalated into a civil war and has claimed more than 36,000 lives, according to a tally by activists.

At the conference in Doha, the SNC will have to decide whether to accept a plan proposed by a prominent dissident, Riad Seif, to set up a new leadership group of about 50 members. The SNC would get some 15 seats, meaning its influence would be diluted, while military commanders and local leaders in rebel-held areas would win wider representation.

Seif said his plan has broad international backing and portrayed it as a stepping stone to more robust foreign aid.

SNC chief Abdelbaset Sieda dismissed Seif's optimism, saying he and others in the SNC no longer trust promises of international support that are linked to restructuring of the opposition.

"We faced this situation before, when we formed the SNC (last year)," he told The Associated Press. "There were promises like that, but the international community in fact did not give us the support needed for the SNC to do its job."

The SNC is to decide Wednesday whether to accept Seif's plan. Sieda said the SNC believes it deserves at least 40 percent of the seats, should it decide to join the new group, suggesting the group may have decided it's under too much pressure to reject the plan entirely.

As opposition leaders haggled in Qatar, activists said rebels captured an oilfield in eastern Syria on Sunday after three days of fighting with government troops, and shot down a Syrian warplane in the area. The Britain-based Syrian Observatory for Human Rights said rebels overran the Al-Ward oilfield in the province of Deir el-Zour near Iraq.

Oil was a major source of revenue for Assad's regime before the U.S. and the European Union imposed an embargo on Syria's crude exports last year, in response to Assad's brutal crackdown on the uprising against him. Syrian officials have accused rebel units of targeting the country's infrastructure, including blowing up the oil and gas pipelines.

Syrian state media, meanwhile, said rebels detonated a car bomb near the Dama Rose hotel in the capital, wounding several people. The hotel has been used in the past by U.N. observers visiting Syria. The reports also said rebels were behind the assassination of a leading member of the ruling Baath party in northeast Raqqa province.

The Syrian opposition leaders met at a luxury hotel in Doha, the capital of the small Gulf state of Qatar that has emerged as a major backer of the Syrian rebels. Organizers said more than 400 delegates are attending four days of internal SNC meetings and will choose new SNC leaders on Tuesday. A day later, the SNC is to vote on Seif's plan.

On Thursday, Seif will attempt to form the new leadership group with the backing of the SNC. If he is successful, the Friends of Syria, an alliance of countries backing the rebels, is to convene in Morocco, he said.

The 66-year-old Seif, who left Syria few months ago after having been detained by the regime, said that if his plan is accepted, "the whole world will be behind" the new opposition leadership.

At the Morocco conference, "maybe 100 countries will recognize this new leadership as the legitimate and only representative of the Syrians," said Seif, who suffers from cancer and is not seeking a leadership role.

He did not say what kind of practical support the opposition could expect, but suggested the Morocco gathering would be a launching pad for a transitional government.

A senior U.S. official has said the Washington did not want to attend another Friends of Syria conference unless the opposition comes up with a new, more representative leadership. Many of the current SNC leaders live in exile, and appear to have little say over the course of the rebellion inside the country.

Sieda bristled as the criticism, saying that "it is unfair to say that the SNC represents (those) outside Syria."

The SNC argues that it represents several dozen groups, including a number based in Syria.

Abdel-Rahman al-Haj, a spokesman for the group, said the international community's criticism of the SNC is meant to deflect from the world's failure to stop the bloodshed in Syria.

"The international community … did not give us any help, support and weapons," he said. "We just hear talking."

Al-Haj, a 41-year-old Syrian exile in Malaysia, said the SNC is considering the possibility of setting up its own transitional government if it decides to reject Seif's plan. However, he said everything is still open to debate.

The disagreements at the conference reinforced doubts in the opposition's ability create a new structure the U.S. and its allies can work with. The U.S. hopes a more representative body can provide a reliable partner, buffer against interference by extremists and help bring Syria's allies Russia and China on board with change.

However, divisions among political leaders are not the only concern.

Rebel fighters are split into small largely autonomous groups, some led by local figures little known outside Syria. Most nominally belong to the umbrella Free Syrian Army, but their ties to it are often just lip-service. In many hotspots, fighters from a radical Islamic group inspired by the al-Qaida terror network have taken on prominent roles.

In his opening speech at the conference, Sieda said the SNC is trying to unify all military groups under one leadership, in part to prevent "any extremism, mistakes or atrocities" from being committed. Earlier this week, a video appeared to show rebel fighters executing a group of unarmed, captured Syrian soldiers, prompting an international outcry.

Sieda urged all commanders and rebel fighters to respect human rights and said those violating them on the rebel side would be brought to justice.